Abstract: In this paper, the duration, range, intensity and influence of low temperature in Inner Mongolia in winter of 2009/2010 were analyzed. The formation causes of low temperature were also analyzed from the aspects of circulation over East Asia, cold air activity over Inner Mongolia, Arctic Oscillation and El Nino. The results show that Inner Mongolia suffered from the most serious low temperature which lasted for the longest period and affected the widest area in winter of 2009/2010 since 1986. Heavy snowfall, strong wind and serious sandstorm occurred when temperature dropped strongly. The low temperature was caused by the stronger Siberian High at surface, stronger northerly flow at 850 hPa over north Inner Mongolia, lower geopotential height at 500 hPa over Inner Mongolia, westward and stronger East Asian Trough at 500 hPa, and more frequent activity of strong cold air current than those in normal years. A statistic result shows that there was a significant positive correlation between Arctic Oscillation Index in winter and winter temperature in Inner Mongolia. A composite analysis reveals that the low temperature occurred in most area of Inner Mongolia in El Nino winter, and this conclusion was different from the achievements in previous studies.

Key words: winter low temperature, air current circulation, Arctic Oscillation Index, El Nino event, Inner Mongolia